Variability of annual sediment load and runoff in the Yellow River for the last 100 years (1919-2018).

The sediment load of the Yellow River, once the highest in the world, has decreased to a record low. The annual sediment load (ASL, t·yr) in the main stream of the Yellow River in the past 100 years (1919-2018) shows that the ASL was consistently high for the first 60 years and then decreased gradually until 1999, when the Green for Grain Project (GGP) launched on the Loess Plateau caused ASL to drop sharply. The annual runoff did not decrease as much as ASL from 1919 to 2018, while it decreased significantly in the middle reaches. With the construction of sediment storage dams, terraces, and reservoirs, especially after the GGP launched, the ASL of the Yellow River has been reduced to historic lows. For example, the annual average Normalized Difference Vegetation Index (NDVI) of the Yellow River Basin increased significantly from 1982 to 2016, and the ASL decreased exponentially with increasing NDVI. Although the annual precipitation has a stationary behavior in the Yellow River, the daily precipitation extremes affecting erosion showed an increase of 7% per degree of warming but did not change the trend of ASL reduction. Therefore, the effective management on the Loess Plateau can control the trend of the sediment load of the Yellow River. Erosion, sediment load, and runoff in changing environments are affected by flood control and drought resistance, so more attention should be paid to these hydrologic processes.